Combined contact and wire terminal



March 27, 1962 D. F. DALY COMBINED CONTACT AND WIRE TERMINAL Filed July 8, 1959 INVENTOR [70/7/6/ F DO/y By his af/ameys Unite tates Patent 3,027,440 COMBINED CONTACT AND WIRE TERMINAL Daniel F. Daiy, Hartford, Conn, assignor to The Arrow- Hart & Hegeman Electric Company, Hartford, Conn, a corporation of Connecticut Filed Juiy 8, 1959, Ser. No. 825,745 2 Claims. (Cl. Nth-166) This invention relates to a combined terminal and contact for carrying heavy currents, and more particularly to a contact for heavy duty knife-blade switches with a terminal combined therewith.

In knife-blade switches for use in electric circuits of high current-carrying values, it is essential to keep the heat rise at all joints, connections and contacts as low as possible. Bearing in mind that the heat loss increases as the square of the current times the resistance, it is obvious that the resistance at the joints, connections and contact surfaces must be kept at a minimum. In other words, since in trying to keep the heat loss low the current cannot be altered from the demands of the circuit, but must be accepted as a quantity not subject to variation for the purpose of keeping down heat loss, it follows that the only remaining factor, i.e. the resistance at the joints and connections, must be kept at minimum value or eliminated, wherever it is possible to eliminate a joint.

Therefore, it is an object of the invention to reduce the contacting and connecting surfaces to a minimum number and to provide large areas of firm contact at the contacting and connecting surfaces such as between the conductor wires and terminal and between the blade and contacts of the switch.

The advantages of the, invention will appear more clearly as it is described in connection with the accompanying drawing.

In the drawing:

FIG. 1 is a perspective view of a combined contact and terminal blade embodied in the invention.

FIG. 2 is a side elevation view, partly in section on line 22 of FIG. 1, of the contact and terminal member as illustrated in FIG. 1.

Referring to the drawing, the contact and terminal comprises two heavy metal stampings 1i and 2t) formed from strips or bars into the shapes shown in the figures of the drawing. The part which hereinafter may be referred to as the first part or blade member, is stamped into L-shape with one arm adapted to lie on an insulating base or other support B and bored for free passage therethrough of a securing screw 37 passing up through the base B. The other arm 12 of this member forms one of a pair of contact jaws and has one of its upper corners bent obliquely outward to guide the switch blade (shown in broken line in FIGURE 2) into engagement with the aw.

The second part 2% (which may be referred to as the terminal member) has a jaw portion 22 facing jaw 12 and has its corner opposite the corner 14 bent obliquely like the corner 14, but in the opposite direction so that it and the corner 14 both cooperate with the switch blade to guide the blade into the jaws.

The jaw 22 is integral with a base portion 23 from which it is bent up at an oblique angle only a few degrees greater than 90 so that it inclines slightly toward the jaw 12. Conversely, the jaw 12 is bent up at an acute angle only a few degrees less than 90 with reference to the base plate portion so as to incline slightly toward the jaw 22. The base portion 23 of the terminal member sits on the base arm 15 of the member 10 and is secured firmly thereto by the screw 37 threaded into a tapped hole in register with the previously mentioned bore of the base arm 15.

The contact surfaces of the jaws 12 and 22 are spaced apart less than the thickness of the switch blade so that the inclination of the jaws toward each other supplies constant strong pressure of the jaws against the opposite sides of the switch blade to insure good contact pressure. To concentrate and thereby increase the pressure per square inch and also to compensate for any slight misalignment of the blade with the jaws, the jaws may have spherical bulges pressed from their contact surfaces toward each other.

To locate the jaw 22 with relation to the jaw 12, the base arm 15 of the member 10 has two round nubs 13 pressed up from its upper surface and received in two round holes 28 in the base portion 23 of the terminal 20.

Extending beyond the base portion 23 of the terminal member and away from the jaw portion 22 is a terminal portion which is bent in three consecutive spaced right angle bends forming a loop or tunnel 25 into which a conductor wire or wires 30 are inserted. In a tapped hole in the top surface 24 of this loop or tunnel, a terminal screw 23 is threaded for securing the connector wire 30 in place and in firm permanent and positive contact with the bottom or base surface 26 of the loop.

The base surface 26 is provided with a tapped hole into which is threaded a securing screw 29 passing upward through the base B for more firmly securing the terminal portion to the base. This is desirable because the conductor wires necessary for circuits carrying heavy currents are thick and not easily bendable and, hence, exert substantial pressures on the terminals to which they are connected.

From the foregoing, it will be understood that the invention comprises only two electrically conductive parts which together cooperate to form contact jaws for the reception of the blade of a knife switch and also to provide a terminal connection by which the heavy conductor wires of high current-carrying capacity are able to be secured or connected to the contact.

Between the conductor wire and terminal there are only two areas of contact which may be completely firm and adequate to conduct the heavy duty currents. Moreover, between the terminal portion of the device and the switch jaws there is only one contacting and connecting surface which is of wide extent and may be very firmly secured by adequate pressure against each other and simultaneously to the base or Whatever member on which the combined contact and terminal is mounted.

The invention moreover provides for maintaining the relationship of one blade to another by registering apertures and nubs and also provides for firm contact pressure and for the possibility of slight misalignment of the blade and contact jaws. This latter feature is of particular importance in combination with the other features of the invention as otherwise the heat rises between the surfaces of the jaws and the switch blade might rise to such a point as to severely reduce the utility or limit the rating of the device, despite the fact that other features of the structure are such as would give it a much higher rating. Thus, all of the various devices embodied in the invention cooperate for the achievement of the desired high conductivity and low heat rise in the combined contact and terminal member which forms the subject of the invention.

Variations in the form and configuration of the parts will appear to those skilled in the art within the scope of the invention. One such variation involves making the two parts It} and 2G in one piece, which may more economically be done in large volume production where higher tool costs become more practical. In the onepiece form. the base surface 26 and base plate portion 15 would join and become one base plate member.

Therefore, the invention is not limited to the precise form of the parts as illustrated and described.

What is claimed is:

1. A contact and terminal combination for electric knife-blade switches of high current-carrying capacity, comprising a first member of L-shape having a jaw portion and a base portion, a second member having a jaw portion facing the jaw portion of the first member and a base portion lying directly upon the base portion of said first member and also having a tunnel portion to one side of theplanes of said jaw portions and adapted to receive a conductor wire, a terminal screw threaded through one wall of said tunnel portion and securing the conductor wire directly against another wall of the tunnel portion, and means to secure said base portions directly against one another and to hold said jaw portions in position to receive a switch blade between them, and means pressed into and from said base portions engaging to locate said jaw portions and maintain their positions relative to each other when said securing means is tight.

2. A contact and terminal combination as claimed in claim 1 wherein said tunnel portion comprises two pairs of parallel walls each connected at least one edge to an adjacent surlace, and one wall being connected to the base portion of the second member as an integral extension therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 817,222 Case Apr. 10, 1906 825,091 Van Nuis July 3, 1906 1,025,245 Cole May 7, 1912 1,551,568 Johnson Sept. 1, 1925 2,371,446 Jensen Mar. 13, 1945 2,374,107 Langford Apr. 17, 1945 FQREIGN PATENTS 172,718 Great Britain M Dec. 12, 1921 944,494 France Nov. 2, 1948 

